133 SUMMARY. CuAr. IV. 



brancli out on all siili^s, and to overtop and kill the surrounding 

 t\vii>s and l)ranchcs, in the same manner as species and groups 

 of speeies have at all times overmastered other species in the 

 great battle for life. The limbs, di\'ided into great branches, 

 and those into lesser and lesser branches, were themselves once, 

 when the tree Avas small, budding twigs ; and this connec- 

 tioTi of the former and present Inids by ramifying branches may 

 well represent the classification of all extinct and living species 

 in groups subordinate to groups. Of the many twigs which 

 nourished when the tree was a mere bush, only two or three, 

 now grown into great branches, yet survive and bear all the 

 other branches ; so with the species which lived during long- 

 ])ast geological periods, very few now have living and modified 

 descendants. From the first growth of the tree, many a limb 

 and branch has decayed and dropped off; and these lost 

 branches of various sizes may represent those whole orders, 

 families, and genera, which have now no living representatives, 

 and whicli are known to us only from being found in a fossil 

 state. As we here and there see a thin, straggling branch 

 sj)ringing from a fork low down in a tree, and which by some 

 chance has been favored and is still alive on its summit, so we 

 occasionally see an animal like the Ornithorh^mchus or Lepi- 

 dosiren, which in some small degree connects by its affinities 

 two large branches of life, and which has apparently been 

 saved from fatal competition by having inhabited a protected 

 station. As buds give rise by growth to fresh buds, and these, 

 if vigorous, branch out and overtop on all sides many a feebler 

 branch, so by generation I believe it has been Avith the great 

 Tree of Life, which fills with its dead and broken branches the 

 crust of the earth, and covers the surface with its ever-branch- 

 inc: and beautiful ramifications. 



